Let's talk about photography today, in this article we will discuss about three important key elements that control the exposure. Well if you don't know what exposure is, A photograph's exposure determines how light or dark an image will appear when it's been captured by your camera. Believe it or not, this is determined by just three camera settings: ISO, Aperture and Shutter Speed (the "exposure triangle"). Mastering their use is an essential part of developing an intuition for photography.

Exposure Triangle

Each setting controls exposure differently:

ISO speed: controls the sensitivity of your camera's sensor to a given amount of light.

Aperture: controls the area over which light can enter your camera.

Shutter Speed: controls the duration of the exposure.

Lets talk about these independently, first the easier one "ISO",

The ISO speed determines how sensitive the camera is to incoming light. Basically, ISO is a physical value that describes the sensitivity to light that can’t be changed when we take photos with films, but thanks to the digital sensor we use today in DSLR cameras and smartphone. We can control ISO by ourselves.

Group of sample images from ISO 100-25600

Here is a group of sample images from ISO 100-25600 I found on the Internet. We can easily see that higher ISO will make the images brighter. Theoretically, the higher number of ISO sensor supports the better, but why smartphones usually support ISO number under 10K? You can also find this answer in this group of samples with different ISO. When the sensor becomes more sensitive to light it also becomes more sensitive to noise signal. You can easily see that ISO 25600 image has so much more noise than ISO 3200 image. This phenomenon also explains that, why images taken in low light conditions with high ISO will have more noise than the images taken during good light.

Let's go to the next term "Aperture",

A camera's aperture setting controls the area over which light can pass through your camera lens. In optics, an aperture is a hole or an opening through which light travels.

Different aperture sizes

Let's see the above image, it shows how aperture changes with the f number (we call it f-stock). The smaller the f number means bigger the aperture size. We should know that in DSLR cameras aperture can be manually changes to adjust different light situatiuons. Being limited by the size of hardware, aperture in samartphones is stable. However, in recent flagship Galaxy smartphones such as S9, S10 you can jump between f/2.4 and f/1.5 aperture size, which is really handy. This tells us that the bigger hole allows more light to go through the lens which make the images brighter.

Here is a comparison of f/2.8 and f/11

Aperture controls another important aspect of camera: Depth of Field (bokeh effect). The larger aperture has shallower Depth of Field, which gives us stronger bokeh effect.

Here is a comparison of Depth of Field between f/1.8 and f/5.6

Finally, let’s talk about "Shutter Speed",

A camera's shutter determines when the camera sensor will be open or closed to incoming light from the camera lens. The shutter speed specifically refers to how long this light is permitted to enter the camera. Basically, shutter speed (exposure time) is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a picture.

Different shutter speeds at same ISO and Aperture

In above example, a group of sample images show that longer exposure time will make the picture brighter while aperture and ISO are the same.

But sometimes we may need slow shutter speed (long exposure time) to achieve the effect we need.

Light Painting (around 20 sec exposure time)

Star Trails Photography (Need several hours exposure time)

There is one more thing we should pay attention to and that is because of human body shaking when we take a photo with exposure time longer than 1/30s, we need an equipment like tripod, which helps us to keep the camera stable. This happens a lot when we take photos during low light situations or take pictures in night mode.

That's all for today, I hope this post explained these three key elements well.

I would like to know what you guys think about this post. Let me know in the comments below!